Boom assembly

ABSTRACT

AN IMPROVED BOOM ASSEMBLY INCLUDES RELATIVELY MOVABLE INNER AND OUTER SECTIONS MOUNTED IN A TELESCOPIC RELATIONSHIP WITH EACH OTHER. A FIRST GROUP OF GUIDE ROLLERS IS MOUNTED ON THE OUTER END OF THE OUTER SECTION OF THE BOOM ASSEMBLY AND IS POSITIONED FOR ROLLING ENGAGEMENT WITH CORNER PORTIONS OF THE INNER SECTION OF THE BOOM ASSEMBLY. A SECOND GROUP OF GUIDE ROLLERS IS MOUNTED ON THE INNER END OF THE INNER SECTION OF THE BOOM ASSEMBLY AND IS POSITIONED FOR ROLLING ENGAGEMENT WITH CORNER PORTIONS OF THE OUTER SECTION OF THE BOOM ASSEMBLY. EACH ROLLER OF THESE GROUPS OF ROLLERS IS ADJUSTABLE   BOTH AXIALLY AND RADIALLY RELATIVE TO THE SECTION OF THE BOOM ASSEMBLY WHICH IT ENGAGES. THIS ENABLES THE ROLLERS TO BE ADJUSTED TO ELIMINATE SIDE LOADING AND TO PROVIDE FOR PROPER TRACKING OR ROLLING OF THE ROLLERS ALONG THE CORNER PORTIONS OF THE ENGAGED SECTIONS. THE ROLLERS ARE ADVANTAGEOUSLY MOUNTED ON BRACKETS WHICH ARE CONSTRUCTED SO AS TO ENABLE THE ROLLERS TO BE READILY MOUNTED ON THE BOOM ASSEMBLY AND INTERCHANGED WITH EACH OTHER.

United States atent [54] BOOM ASSEMBLY 15 Claims, 11 Drawing Figs.

(52] U.S.Cl 2l4/l4lt 52/118.52/12!.52/632,2l2/55,2l4/l38 [5 l] Int. Cl [302i 9/14 2l4/l4l,

[50] Fieldol'Search l38;2l2/55;52/ll8,l2l,632,645.646

[56] References Cited UNITED STATES PATENTS 2,339,327 1/1944 Fox 52/l2lX 2,833,422 5/1958 Ferwerda et al. 212/55 3,224,608 12/1960 Yadon et al. 214/141 Primary Examiner Robert G. Sheridan Assistant Exammer- Frank E. Werner Attorney- Yount, Flynn & Tarolli ABSTRACT: An improved boom assembly includes relatively movable inner and outer sections mounted in a telescopic relationship with each other. A first group of guide rollers is mounted on the outer end ofthe outer section of the boom assembly and is positioned for rolling engagement with corner portions of the inner section of the boom assembly. A second group of guide rollers is mounted on the inner end of the inner section of the boom assembly and is positioned for rolling engagement with corner portions of the outer section of the boom assembly. Each roller of these groups of rollers is adjustable both axially and radially relative to the section of the boom assembly which it engages. This enables the rollers to be adjusted to eliminate side loading and to provide for proper tracking or rolling of the rollers along the corner portions of the engaged sections. The rollers are advantageously mounted on brackets which are constructed so as to enable the rollers to be readily mounted on the boom assembly and interchanged with each other.

PATENTEU JUN28 I97! SHEU 1 (1F 3 lNl/ENTURS JOHN W EFINE] LESTER H.KL|NE PATENTEU JUH28 19v:

SHEET 3 OF 3 BOOM ASSEMBLY This invention relates generally to a boom assembly and more particularly to a boom assembly having telescoping sections with guide rollers whose positions are adjustable both sidewardly and in and out relative to an engaged section of the boom assembly.

A known boom assembly includes a pair of telescopically mounted sections with guide rollers which engage corner portions on each of the sections to facilitate relative movement between the sections. Heretofore, these guide rollers have been adjustable only in a radial direction relative to the engaged corner portions of the boom assembly to adjust the clearance between the rollers and the engaged corner portions. While this known boom assembly has been generally satisfactory, difficulty has been encountered due to axial or sideward misalignment of the rollers and the engaged corner portions of the boom .assembly. This axial or sideward misalignment has resulted in side loading and uneven wearing of the rollers.

Accordingly, it is an object of this invention to provide a new and improved boom assembly having telescopically mounted sections with rollers which are adjustable both radially and axially relative to an engaged section of the boom assembly.

Another object of this invention is to provide a new and improved boom assembly having telescopically mounted sections with rollers which engage corner portions of these sections and are readily adjusted both radially and axially relative to the engaged corner portions while the boom assembly is in an operative or assembled condition.

Another object of this invention is to provide a new and improved boom assembly having telescopically mounted sections with rollers thereon to facilitate relative movement between the sections and wherein each of the rollers is readily adjusted along at least two axes to compensate for wear of the roller and manufacturing error in the shape ofthe sections.

Another object of this invention is to provide a new and improved boom assembly having telescopically mounted sections with corner portions which are engaged by rollers mounted on the sections to facilitate relative movement between the sections and wherein the rollers are readily aligned with the corner portions to prevent improper tracking and side loading of the rollers.

Another object of this invention is to provide a new and improved boom assembly having telescopically mounted sections with rollers mounted on the sections by a plurality of brackets which are interchangeable to enable the rollers to be mounted at a plurality of locations on the boom assembly.

Another object of this invention is to provide a new and improved boom assembly having telescopically mounted sections with a first group of rollers mounted on a first section engaging a second section and a group of rollers mounted on the second section engaging the first section wherein at least one roller in the first group of rollers is readily interchangeable with at least one roller in the second group of rollers.

Another object of this invention is to provide a new and improved boom assembly having telescopically mounted sections with rollers thereon to facilitate relative movement between the sections and wherein the rollers are mounted on brackets to enable them to be mounted on the sections as units which are readily adjustable relative to the sections and easily replaced when necessary.

These and other objects and features of the invention will become more apparent upon the consideration of the following description taken in connection with the accompanying drawings wherein:

FIG. 1 is a schematic illustration of a machine having a boom assembly constructed in accordance with the present invention;

FIG. 2 is an enlarged fragmentary view of the boom assembly of FIG. 1 in a horizontal position;

FIG. 3 is an enlarged, partially broken away sectional view, taken generally along the line 3--3 of FIG. 2, illustrating the relationship of rollers mounted on a main or outer section of section of the boom assembly;

FIG. 6 is a schematic illustration, generally similar to FIG. 5, illustrating the manner in which rollers mounted on the outersection of the boom assembly are adjusted in a second direction relative to the inner section of the boom assembly;

FIG. 7 is a schematic illustration depicting the manner in which rollers mounted on the outer section of the boom assembly are adjusted in both the first and second directions relative to the inner section of the boom assembly;

FIG. 8 is a schematic illustration depicting the manner in which a roller mounted on the inner section of the boom as sembly is adjusted in a radially outward direction;

FIG. 9 is a schematic illustration, generally similar to FIG. 8, depicting the manner in which a roller mounted on the inner section of the boom assembly is adjusted in an axial or sideward direction;

FIG. 10 is a schematic illustration depicting the manner in which a roller mounted on the inner section of the boom assembly is adjusted in both the axial and radial directions; and

FIG. 11 is a sectional view, taken generally along the line 11-11 of FIG. 3, illustrating the relationship between rollers mounted on the outer section of the boom assembly and a plurality of shims for adjusting the positions of the rollers relative to the inner section of the boom assembly.

The present invention relates to a boom assembly having sections mounted for telescopic movement relative to each other. This movement is facilitated by rollers which are mounted on one section for rolling engagement with another section. In accordance with the present invention, these rollers are adjustable both axially and radially to eliminate side loading of the rollers and to provide for proper tracking or rolling of the rollers along the engaged section of the boom assembly upon relative movement between the sections. The rollers are adjusted relative to the engaged section by the use of shims to selectively vary the positions of the rollers in axial and/or radial directions.

Although a boom assembly 20 constructed in accordance with the present invention can be utilized in many different environments, it is illustrated in FIG. 1 in association with a known type of excavating machine 22 having a base 24. The boom assembly 20 includes a main or outer section 28 which is connected to the base 24 and a telescoping or inner section 30 which is mounted for telescopic movement relative to the main section 28. In the illustrated embodiment of the invention, an earth-working implement or bucket 34 is connected to an outer end portion of the boom assembly 20. The implement 34 is moved relative to the base 24 by telescopic movement of the inner section 30 relative to the outer section 28 under the influence of a known drive mechanism, such as a hydraulic cylinder 32 (FIG. 2).

To facilitate telescopic movement between the sections 28 and 30, a first or outer group 36 (FIG. 3) of rollers is mounted at an end portion 38 of the outer section 28. The group 36 of rollers includes rollers 40, 42, 44, 46 and 48 which engage corner portions 50, 52 and 54 of the inner section 30 to guide and support the inner section as it is moved relative to the outer section 28. A second or inner group 60 of rollers is mounted at an end portion 62 (see FIG. 4) of the inner section 30. This second group 60 of rollers also guides the inner section 30 as it is moved telescopically relative to the outer section 28 of the boom assembly 20 and includes rollers 66, 68 and 70. These rollers are rotatably mounted at corner portions of the inner section 30 and engaged corner portions 74, 76

and 78 ofthe outer section 28. During telescopic movement of the inner section 30 relative to the outer section 28, the rollers 40-48 track or roll along the corner portions 50-54 of the inner section while the rollers 66-70 track or roll along the corner portions 74-78 of the outer section to guide the movement of the inner section.

To enable the boom assembly 20 to be readily operated between a retracted condition and an extended condition by telescopic movement of the inner section 30 relative to the outer section 28, the first group 36 of rollers must roll freely along the corner portions 50-54 of the inner section while the second group 60 of rollers rolls along the corner portion 74-78 of the outer section. If the two groups 36 and 60 of rollers are improperly aligned with the associated corner portions of the inner and outer sections 30 and 28, the rollers tend to cause a twisting or flexing of the inner section as it is moved relative to the outer section. This twisting or flexing of the inner section 30 impedes the relative movement between the inner and outer sections of the boom assembly and subjects the rollers 40-48 and 66-70 to unnecessary wear inducing forces. These rollers are also subjected to unnecessary wear when they apply excessive pressure against the associated corner portions of the inner and outer sections 30 and 28. Of course, the clearance between the rollers and the associated corner portions ofthe inner and outer sections 30 and 28 must not be so great as to allow the inner section of the boom assembly 20 to move sidewardly in an unrestrained manner relative to the outer section.

In accordance with a feature of the present invention, the rollers 40-48 and 66-70 are adjustable axially or sidewardly and radially or in and out. These adjustments can be combined to provide for simultaneous axial and radial adjustment of the rollers. The capability for axial adjustment enables the rollers to be aligned with the associated corner portions of the inner and outer sections 30 and 28 of the boom assembly 20. The capability for radial adjustment enables a desired amount of clearance to be provided between the rollers and the associated corner portions.

To provide for radial and axial adjustment, the rollers 40 and 42 are mounted in a set on a common bracket 84. The bracket 84 has flat-locating surface portions 86, 88, 90 and 92 which cooperate with similar flat supporting surface portions 96, 98, 100 and 102, respectively, (see FIGS. 3 and Inserts or shims 106, 108, 110 and 112 are initially positioned between associated locating surfaces 86, 88, 90 and 92 and support surfaces 96, 98, 100 and 102. These shims position the rollers 40 and 42 to provide a desired amount ofclearance between the corner portion 50 of the inner section 30 and the rollers 40 and 42.

After a period ofoperating the excavating machine 22, wear of the roller 42 or corner portion 50 may increase the clearance between the roller and corner portion. To compensate for this increased clearance, it is necessary to adjust the roller 42 radially inwardly by moving the roller inwardly along a radial axis extending through a point of engagement of the roller and the corner portion 50. To do this, it is merely necessary to insert additional shims 118 and 120 between the locating surfaces 88 and 92 and the support surfaces 98 and 102 in the manner illustrated schematically in FIG. 5. These shims move the roller 42 radially inwardly, that is in the direction of the arrow 124, to compensate for the wear of the roller and corner portion 50. Of course, the shims 118 and 120 could be inserted between the locating surfaces 88 and 92 and the support surfaces 98 and 102 during initial fabrication ofthe boom assembly to compensate for manufacturing error in the shape ofeither the inner or outer sections 30 or 28.

To increase the clearance between the roller 42 and corner portion 50 from the clearance provided in the initial condition of FIG. 3, it is merely necessary to remove the two shims 108 and 112 from between the locating surfaces 88 and 92 and the support surfaces 98 and 102. Removal of these shims results in the roller 42 moving radially outwardly, that is in a direction opposite from the arrow 124 of FIG. 5. To facilitate precise adjustment of the roller 42, it is contemplated that a plurality of relatively thin shims will be initially provided between the locating surfaces 88 and 92 and the support surfaces 98 and 102. However, for purposes of clarity of illustration, only a single shim is shown in the drawings to represent the presence or insertion of what will probably be many thin shims.

The insertion of the additional shims 118 and adjusted the roller 42 in a radial direction and at the same time adjusted the roller 40 in an axial or sideward direction. This axial adjustment of the roller 40 maintains the roller 40 in alignment with the corner portion 50 of the inner section 30. The roller 40 is advantageously provided with a generally circular outer surface which remains in engagement with the corner portion 50 even through theclearance between the roller 42 and the corner portion 50 may tend to vary.

If the roller 40 or corner portion 50 should wear in such a manner as to increase the clearance between the roller 40 and the corner portion, the roller 40 must be adjusted radially inwardly to offset the increase in clearance. This is accomplished by inserting additional shims 134 and 136 (FIG. 6) between the locating surfaces 86 and 90 and the support surfaces 96 and 100. Insertion of these shims moves the bracket 84 in the direction of the arrow 138 to compensate for the increased clearance.

It is is desired to increase the clearance between the roller 40 and the corner portion 50 from the condition illustrated in FIG. 3, the shims 106 and 110 are removed. The bracket 84 is then moved outwardly in a direction opposite to the arrow 138 of FIG. 6. It should be noted that while the roller 40 is moved radially by varying the number of shims between the locating surfaces 86 and 90 and the support surfaces 96 and 100, the roller 42 is axially or sidewardly aligned relative to the corner portion 50 by movement of the bracket 84. The roller 42 is also provided with a generally circular outer surface 140 which engages the corner portion 50 even though the clearance between the roller 42 and corner portion 50 may tend to vary.

Under certain circumstances, such as when there has been a wearing of both the rollers 40 and 42, it may be desired to adjust both of the rollers sidewardly and inwardly in the general direction of the arrow 144 ofFlG. 7. This sideward and inward movement of both of the rollers is accomplished by inserting additional shims 146, I48, and 152 between all of the locating surfaces and support surfaces, that is between locating surfaces 86-92 and the associated support surfaces 96-102. The extent to which either of the rollers 40 or 42 is adjusted inwardly can be changed by varying the number of shims between two of the locating surfaces and two of the support surfaces. For example, ifit was desired to adjust the roller 40 inwardly for a greater distance than the roller 42, two additional shims would be inserted between the locating surfaces 86 and 90 and the support surfaces 96 and 100 while one additional shim would be inserted between the locating surfaces 88 and 92 and the support surfaces 98 and 102.

The rollers 44 and 46 are mounted on a common bracket 153 (FIG. 3) in much the same manner as in which the rollers 40 and 42 are mounted on the bracket 84. The brackets 84 and 153 are substantially identical in structure. However, an end plate has been removed from the bracket 84 in FIG. 3 to more clearly illustrate the mounting of the rollers 40 and 42. The rollers 44 and 46 are adjusted relative to the corner portion 52 by inserting varying numbers of shims between locating surfaces on the support bracket 153 and support surfaces on the outer section 28. Therefore, it is believed that it will be apparent from the foregoing description that the rollers 44 and 46 can be adjusted both radially and axially relative to the corner portion 52 in much the same manner as in which the rollers 40 and 42 are adjusted relative to the corner portion 50.

The second or inner group of rollers 60 (FIG. 4) is adjustable relative to the corner portions 74-78 of the outer section 28 to enable these rollers to be properly aligned with the corner portions and to provide the desired amount of clearance between the rollers and the corner portions. Thus, the roller 70 is adjustable in both an axial or sideward direction and in a radial direction relative to the corner portion 78. To provide for this adjustment of the roller 70, the

roller is mounted on a bracket 154 at a corner portion 54 of 5 the inner section 30 of the boom assembly 20. When the boom assembly is initially fabricated, shims 158 and 160 are mounted between locating surfaces 164 and 166 on the bracket 154 and support surfaces 168 and 170 on the inner section 30 ofthe boom assembly 20.

The support surfaces 168 and 170 are spaced-apart and slope inwardly to define a recess for receiving the bracket 154 on which the similarly sloping locating surfaces 164 and 166 are formed. To compensate for wear of the roller 70 or the corner portion 78, the roller 70 is adjusted radially outwardly in the direction of the arrow 174 in FIG. 8. To accomplish this outward adjustment of the roller 70, additional shims 178 and 180 (FIG. 8) are inserted between the locating surfaces 164 and 166 and the support surfaces 168 and 170. These shims move the roller 70 outwardly along a radial axis through a point ofengagement ofthe roller-and the corner portion 78.

If the roller 70 is side loaded, it will wear excessively along one ofthe sides 184 or 186 ofan annular groove 188 (see FIG. 4) which engages the corner portion 78. The roller 70 is adjustable axially or sidewardly to compensate for this wear and to properly align the roller 70 with the corner portion 78 to thereby eliminate side loading of the roller. Thus if the side portion 184 of the groove 188 is excessively worn, the roller is adjusted axially or sidewardly to the left as viewed in FIGS. 4 and 9. This is achieved by removing the insert 158 from between the support surface 168 and locating surface 164 and inserting an additional shim 192 between the locating surface 166 and support surface 170 in the manner illustrated sche matically in FIG. 9.

The foregoing sideward or axial adjustment ofthe roller 70 is accomplished without changing the position of the roller radially relative to the corner portion 78. This is because the transverse or axial distance between the outer surface of the additional shim 192 (FIG. 9) and the locating surface 168 is the same as the transverse or axial distance between the outer surfaces of the shims 158 and 160 of FIG. 4. Therefore, the roller 70 is adjusted axially in the direction ofthe arrow 194 in FIG. 9 without radial movement of the roller. Of course, the roller 70 can be moved in the opposite direction, that is toward the right as viewed in FIG. 4, by removing the shim 160 from between the locating surface 166 and the support surface 170 and inserting an additional shim between the locating surface 164 and support surface 168.

It is contemplated that in certain situations the roller 70 will wear in such a manner as to require both radial and axial ad justment. Assuming that the roller 70 wears in such a manner as to require adjustment outwardly and toward the left, as viewed in FIG. 4, additional shims 196 and 198 (FIG. 10) are inserted between the locating surfaces 164 and 166 and the support surfaces 168 and 170 to effect a radially outward adjustment of the roller. An additional shim 200 is also inserted between the locating surface 166 and support surface 170 to effect the required sideward adjustment of the roller 70. The combined effect of these shims results in the roller 70 being moved outwardly and sidewardly in the direction of the arrow 202 of FIG. 10.

The rollers 66 and 68 are rotatably mounted on brackets 204 and 205 which are identical in structure to the bracket 154. Therefore, it is apparent from the foregoing description that the rollers 66 and 68 can be adjusted either radially or axially by the use ofshims in much the same manner as was explained in connection with the roller 70. It should be noted that the rollers 66, 68 and 70 are individually adjustable to enable them to be properly aligned with the associated corner portions 74, 76 and 78 and to provide a desired amount of clearance between the rollers and the corner portions.

The first group of rollers 36 includes a single roller 48 which is mounted opposite to the rollers 40 through 46. The roller 48 is mounted on a bracket 206 which is identical to the bracket 154. However, the bracket 206 is positioned with locating surfaces 208 and 210 facing outwardly toward inwardly facing support surfaces 212 and 214 on the outer section 28 of the boom assembly 20. Shims 216 and 218 are positioned between the locating surfaces 208 and 210 and the support surfaces 212 and 214 to locate the roller 48 in the initial position of FIG. 3. The roller 48 can be adjusted relative to the corner portion 54 by the use of additional shims between the locating and support surfaces in much the same manner as previously explained in connection with the roller 70.

The shims are all clamped securely in place between the support and loading surfaces by the same screws used to mount the roller brackets on the inner and outer sections 30 and 28 of the boom assembly. Thus, the shim 106 (FIG. 3) is pressed between the locating surface 86 and support surface 96 by suitable cap screws 220 and 222 FIGS. 2 and 11) which extend through holes in a support member 223 on which the support surface 96 is formed. The screws 220 and 222 engage internal threads on the outwardly projecting section 224 of the bracket 84 to secure the shim 106 and the bracket 84 to the support member 223. To release the shim 106, the screws 220 and 222 are loosened and a jack screw 230 tightened to move the portion 224 of the bracket 84 away from the support surface 96.

It is contemplated that the rollers on the inner and outer sections 30 and 28 will tend to wear and require adjustment after the boom assembly 20 has been used for a substantial period of time. To facilitate this adjustment, the shims can be inserted or removed without dismantling the boom assembly 20. To this end, the shim 106 includes a plurality of open ended slots 234. These slots 234 enable the shim 106 to be pulled upwardly, as viewed in FIGS. 3 and 11, to remove the shim from between the support surface 96 and the locating surface 86 after the cap screws 220 and 222 have been loosened and the jack screw 230 tightened. Of course, shims having similar slots can be readily inserted between the locating surface 86 and support surface 96. Once the desired number of shims have been positioned between the locating surface 86 and support surface 96, the jack screw 230 is released and the cap screws 220 and 222 are tightened to clamp the shims between the loading surface 86 and support surface 96.

The shim 112, between the locating surface 92 and support surface 102, is similar to the shim 106 and is secured and released in the same manner. Since the shim 112 is ofthe same configuration as the shim 106, it is apparent that this shim can also be removed from between the locating surface 92 and support surface 102 while the boom assembly 20 is in the assembled or operative condition. Of course, the other shims associated with the locating surfaces 86 and 92 and the support surfaces 96 and 102, that is the shims 120, 134, 146 and 152 (see FIGS. 5, 6 and 7) are ofthe same configuration illustrated in FIG. 11 for the shim 106.

The shim 110 (see FIGS. 3 and 11) is clamped between the locating surface and support surface 100 in much the same manner as in which the shim 106 is clamped between the locating surface 96 and support surface 96. Accordingly, a pair of capscrews 240 and 242 (FIG. 2) extend through suitable holes in a support section 244 (FIG. 3) into threaded engagement with the bracket 84. By tightening the capscrews 240 and 242, the shim 110 is securely retained in place. When the shim 110 is to be removed or additional shims inserted between the locating surface 90 and support surface 100, the capscrews 240 and 242 are loosened and a jack screw 248 (FIG. 2) is tightened to press the locating surface 90 away from the support surface 100 to release the shim 110 and enable additional shims to be inserted between the locating and support surfaces.

The shim 110 has an open ended slot 252 (FIG. 11) which enables the shim 110 to be removed from between the locating and support surfaces after the capscrews 240 and 242 have been loosened and the jackscrew 248 tightened. Of course, if

surface 98 in the same manner as the shim 110 when the boom assembly is in the operative or assembled condition of FIG. 1. The shims associated with the rollers 44 and 46 are identical in shape to the shims 106 and 110 (see FIG. 11) and are located in corresponding positions relative to the rollers 44 and 46 to enable them to be inserted and removed without disassembling the boom assembly 20.

The shims 158 and 160 associated with the bracket 154 are substantially identical in shape to the shim 106 (see FIGS. 4 and 11). The shim 160 is clamped between the locating surface 166 and support surface 170 by a pair of capscrews 260 and 262 (FIG. 2) which are threaded into the bracket 154. The shim 160 can be removed from between the locating surface 166 and support surface 170 and additional shims inserted by loosening the cam screws 260 and 262 and tightening a jackscrew 266 to move the bracket I54 away from the support surface 170. The outer section 28 of the boom assembly 20 is advantageously provided with a plurality of openings or holes 270 (FIG. 2) through which the capscrews 260 and 262 and jackscrews 266 can be operated when the boom assembly is in the operative or assembled condition of FIG. 1. The openings 270 are sufficiently large to enable the shim 158 to be withdrawn or additional shims inserted without dismantling the boom assembly 20. Of course, the shims as sociated with the rollers 66 and 68 are similar to the shim 160 and can be readily inserted or removed through the openings 270 in the outer section 28.

During operation of the excavating machine 22, certain of the rollers in the boom assembly 20 will be subjected to relatively large loads while other rollers will be subjected to relatively light loads. Of course, this difference in loading results in different rates of wear for the rollers Accordingly, the brackets are advantageously constructed in such a manner as to enable lightly loaded rollers to be interchanged with heavily loaded rollers to thereby distribute the wear more evenly between the rollers. For example, the rollers 42 and 44 (see FIG. 3) will be subjected to a relatively heavy loading during operation of the boom assembly 20 and the rollers 40 and 46 will be subjected to a relatively light loading.

To enable the rollers 42 and 44 to be interchanged with the rollers 40 and 46, the bracket 84 for the rollers 40 and 42 is substantially identical in structure with the bracket 153 for the rollers 44 and 46 and is symmetrical about an axis extending between the rollers 40 and 42. This symmetry of bracket structure enables the rollers 40 and 42 to be interchanged with the rollers 44 and 46 by merely interchanging the brackets 84 and 153. When the rollers are interchanged in this manner, the roller 42 is located where the roller 46 is shown in FIG. 3 and is subjected to a relatively light load. The roller 40 is located where the roller 44 is shown in FIG. 3 and is subjected to a relatively heavy load. Similarly, the interchange of rollers results in the roller 44 being positioned where the lightly loaded roller 40 is shown in FIG. 3 with the roller 46 in position of the roller 42. Thus, the two sets of rollers at the corner portions 74 and 76 of the outer section 28 can be in terchanged to more evenly distribute wear between the rol lers.

Since the single rollers 48, 66. 68 :md 70 (sec FIGS. 3 and 4) are mounted on brackets which are identical in structure, these rollers can all be interchanged. 'lhus, the roller 68 ofthe inner group 60 of rollers can be interchanged for the roller 48 of the outer group 36 of rollers or cart be interchanged with any other roller of the inner group of rollers. In addition. the bracket 154 is symmetrical about a central axis 280 to enable the roller to be rotated l80 from the position shown in FIG. 4 to reverse the positions ofthe side portions 184 and 186 ofthe annular groove 188. Therefore, if the roller 70 should be excessively worn on one side of the annular groove 188 by side loading, the roller can be rotated about the central axis 280 to more evenly distribute the wear on the roller. Of course, the rollers 48, 66 and 68 can be similarly rotated.

In view of the foregoing remarks, it can be seen that the boom assembly 20 includes telescopically mounted sections 28 and 30 with a first group of rollers 36 mounted on the outer section 28 for engagement with the corner portions of the inner section 30. A second group of rollers is mounted on the inner section 30 and engages the outer section 28 to further facilitate relative movement between the two sections. The rollers are adjustable both radially and axially to compensate for manufacturing error in the shape of sections and for wear ofthe rollers and corner portions of the sections. To provide for this radial and axial adjustment of the rollers, the rollers are mounted on brackets which are secured to the sections of the boom assembly. The positions of the brackets can be changed by using shims to compensate for manufacturing error in the shape ofthe sections and for wear of the rollers or the sections. In addition, the shims enable the rollers to be aligned with the associated corner portions which they engage to eliminate improper tracking and side loading of the rollers.

To facilitate adjusting the position ofthe rollers to compensate for wear, the shims have open ended slots which enable them to be inserted and removed from between the locating and support surfaces with the boom assembly in its operative or assembled condition. Although a relatively small number of shims have been shown herein in association with the brackets and rollers for the purposes of clarity of illustration, it is con templated that a large number of relatively thin shims will be associated with each of the brackets and rollers when they are in their initial positions illustrated in FIGS. 3 and 4. In addi tion, while the shims have all been shown as having substantially the same thickness it should be understood that the shims have different thickness and could, ifdesired, be used.

The rollers are advantageously mounted on brackets having the same construction to enable the rollers to be interchanged to thereby distribute wear more evenly between the rollers. Thus. the single rollers 48, 66, 68 and are all mounted on identical brackets so that any of these rollers can be interchanged with any other single roller. The rollers 40 and 42 are mounted on a set on a common bracket 84 and interchangeable with the rollers 44 and 46 on the common bracket 153. In addition to facilitating interchanging of the rollers, the mounting of the rollers on brackets enables them to be quickly and easily bolted in place during fabrication of the boom assembly 20 and subsequently replaced if, after a period ofuse, it becomes necessary to do so.

We claim:

1. A boom assembly comprising a plurality of sections mounted for telescopic movement relative to each other, a plurality of rollers rotatably mounted on one of said sections and having generally annular outer surfaces for engaging surfaces of another of said sections to facilitate relative movement between said sections, and means for selectively adjusting the positions of said generally annular outer surfaces of said rollers in axial directions relative to said surfaces of said other section and for selectively adjusting the positions of said generally annular outer surfaces of said rollers in radial directions relative to said surfaces of said other section to thereby enable said rollers to be adjusted both sidewardly and in and out relative to said other section to provide for a desired rolling relationship of said rollers with said surfaces of said other section during relative movement between said one section and said other section.

2. A boom assembly as set forth in claim I further including at plurality of brackets connected to said one section for mounting said rollers on said one section in a plurality of sets of rollers. said means for adjusting the positions of said antitrlar surfaces of said rollers including means for selectively adjusting the positions of each one of said brackets along a first axis extending generally perpendicular to an axis of rotation of one roller of the set of rollers mounted on said one bracket and for selectively adjusting the position of said one bracket along a second axis extending generally perpendicular to an axis of rotation of another roller of the set of rollers mounted on said one bracket.

A boom assembly as set forth in claim 1 further including a plurality of brackets for mounting said rollers on said one section, said means for adjusting the positions of said annular surfaces of said rollers including means for selectively adjusting the position of each one of said brackets along first and second axes extending transversely to each other and to an axis of rotation of a roller mounted on said one bracket.

4. A boom assembly as set forth in claim 1 further including a plurality of brackets for mounting said rollers on said one section, each of said brackets being mountable on said one section in a plurality of positions to enable each of said rollers to be mounted in a plurality of positions relative to said other section.

5. A boom assembly as set forth in claim 4 wherein said brackets are interchangeable with each other to enable each of said rollers to be mounted on said one section at a plurality of positions.

6. A boom assembly as set forth in claim 4 wherein each one of said brackets is rotatable between first and second positions about an axis transverse to the axis of rotation of a roller mounted on said one bracket, said roller mounted on said one bracket being located in a first relationship with said other section when said one bracket is in said first position and in a second relationship with said other section when said one bracket is in said second position.

7. A boom assembly as set forth in claim 1 further including a plurality of rollers rotatably mounted on said other section and having generally annular outer surfaces for engaging surfaces of said one section to further facilitate relative movement between said sections, and means for selectively adjusting the positions of said generally annular outer surfaces of said rollers mounted on said other section in axial directions relative to said surfaces of said one section and for selectively adjusting the positions of said generally annular outer surface of said rollers mounted on said other section in radial directions relative to said surfaces of said one section to thereby enable said rollers mounted on said other section to be adjusted both sidewardly and in and out relative to said surfaces of said one section to provide for a desired rolling relationship of said rollers mounted on said other section with said surfaces of said one section during relative movement between said one section and said other section.

8. A boom assembly as set forth in claim 7 further including a first group of brackets connected to said one section for rotatably mounting rollers on said one section and a second group of brackets connected to said other section for rotatably mounting rollers on said other section, at least one of said brackets of said first group of brackets being interchangeable with at least one of said brackets of said second group of brackets to enable a roller mounted on said one section to be readily mounted on said other section and to enable a roller mounted on said other section to be readily mounted on said one section.

9. A boom assembly comprising a plurality of sections mounted for telescopic movement relative to each other, one of said sections having a plurality of longitudinally extending corner portions, a plurality of rollers each of which is mounted on another of said sections and engages a corner portion of said one section to facilitate relative movement between said sections, and means for adjusting the position of each one of said rollers along a first axis extending through an associated corner portion of said one section and a point of engagement between said one roller and the associated corner portion and along a second axis extending through said one roller transver sely to said first axis to thereby enable each one of said rollers to be positioned in a desired relationship with the associated corner portion of said one section.

10. A boom assembly as set forth in claim 9 further including a plurality of brackets for mounting said rollers on said other section, said means for adjusting the positions of each one of said rollers including shim means for use in varying the positions of said brackets and rollers relative to said one section.

11. A boom assembly as set forth in claim 10 wherein said other section includes a plurality of sloping support surfaces defining a plurality of tapering recesses each of which is located at a different one of said corner portions of said other section, said shim means being located between said support surfaces and said brackets to enable the positions of said brackets to be varied relative to said recesses and said one section.

12. A boom assembly as set forth in claim 10 wherein a plurality of said rollers are mounted on one of said brackets which has a plurality of locating surfaces each of which extends transversely to an axis of rotation of one of the rollers mounted on said one bracket, said other section including a plurality of support surfaces whichare complimental to locating surfaces on said one bracket, and said shim means includes a plurality of shim elements each of which is positioned between a locating surface of said bracket and a support surface of said other section to position said plurality of rollers mounted on said one bracket relative to said one section 13. A boom assembly as set forth in claim 9 further including a plurality of brackets each of which mounts a plurality of said rollers on said other section, each of said brackets being interchangeable with another of said brackets to enable said rollers to be readily mounted at a plurality of locations on said other section to thereby enable the rollers at one location on said other section to be substituted for rollers at another location on said other section to compensate for any tendency of one of the rollers to wear at a relatively fast rate compared to the other rollers due to an uneven distribution of operating loads between the rollers.

14. A boom assembly comprising a plurality of sections mounted for telescopic movement relative to each other,'each of said sections having a plurality of longitudinally extending corner portions, a first group. of rollers each of which is mounted at a corner portion of one of said sections and has a generally annular outer surface for engaging a corner portion of another of said sections to facilitate relative movement between said sections, a second group of rollers each of which is mounted at a corner portion of said other section and has a generally annular outer surface for engaging a corner portion of said one section to further facilitate relative movement between said sections, first means for adjusting the positions of each roller of said first group of rollers in a direction along its axis of rotation to thereby enable the annular outer surfaces of said first group of rollers to be moved into alignment with associated corner portions of said other section and for adjusting the positions of each roller of said first group of rollers in a direction along an axis extending through the associated corner portions of said other section and a point of engagement between the annular outer surface of the roller and the associated corner portion of said other section to thereby enable the annular outer surfaces of said first group of rollers to be moved into a desired pressure relationship to the corner portions of said other section, and second means for adjusting the positions of each roller of said second group of rollers in a direction along its axis of rotation to thereby enable the annular outer surfaces of said second group of rollers to be moved into a desired alignment with associated corner portions of said one section and for adjusting the positions of each roller of said second group of rollers in a direction along an axis extending through the associated corner portion of said one sec tion and a point of engagement between the annular outer surface of the roller and the associated corner portion of said other section to thereby enable the annular outer surfaces of said second group of rollers to be moved into a desired pressure relationship with the corner portions of said one section.

15. A boom assembly comprising a plurality of sections mounted for telescopic movement relative to each other, each of said boom sections having longitudinally extending corner portions, a bracket mounted at a corner portion of one of said boom sections, a first roller rotatably mounted on said bracket for rotation about a first axis, a second roller rotatably mounted on said bracket for rotation about a second axis which is perpendicular to said first axis, said first and second rollers having generally cylindrical outer surfaces disposed in rolling engagement with one corner portion of another of said boom sections, first shim means for selectively adjusting the position of said first roller in a radial direction relative to said one corner portion of said other boom section and for simultaneously therewith adjusting the position of the generally cylindrical outer surface of said second roller in an axial direction relative to said one corner portion of said other boom section, and second shim means for selectively adjusting the position of said second roller in a radial direction relative to said one corner portion of said other boom section and for simultaneously therewith adjusting the position of the generally cylindrical outer surface of said first roller in an axial direction relative to said one corner portion of said other boom section. 

